JP3586685B2

JP3586685B2 - Vertical stirrer

Info

Publication number: JP3586685B2
Application number: JP10823595A
Authority: JP
Inventors: 隆一弥富; 正文倉津; 仁美佐藤; 幸夫古藪
Original assignee: 住重機器システム株式会社
Priority date: 1995-04-09
Filing date: 1995-04-09
Publication date: 2004-11-10
Anticipated expiration: 2019-11-10
Also published as: JPH08281089A

Description

【０００１】
【産業上の利用分野】
本発明は、各種の流体，半流体，粉体等の槽内撹拌に用いられる撹拌装置、特に、液深Ｈと槽内径（直径）Ｄとの比が１．５以上の高液深タイプおよび粘度領域が概略２．０〜３．０Ｐａ・ｓ以上である高粘度タイプの竪形撹拌機に関する。
【０００２】
【従来の技術】
この種の竪形撹拌装置は一般に、撹拌槽内の中心に撹拌翼をもつ回転軸を外部から回転させ、回転する撹拌翼と、その回転により発生する流体の流動の相互作用により流体の均一混合を行うものである。また、槽内壁には槽内液と前記撹拌翼との共廻りを防止すると共に流体の回転流動を上下流動に変換させるために、通常、槽内径の５〜１５％幅の邪魔板（バッフル）が２〜４枚以上周方向に離隔して取り付けられている。
【０００３】
従来、竪形撹拌装置においては、撹拌槽を高圧容器とした場合の槽板厚負担の低減および反応容器を兼ねる場合の伝熱面積の増大を図り、かつ、大形槽でもできる限り設置面積を小さくするために、槽内径Ｄに対し槽の高さを大とした高液深タイプ（液深Ｈ／槽内径Ｄが１．５以上）のものが知られている。このような高液深タイプあるいは被処理流体が高粘度流体の場合は、撹拌力を強化するために翼の回転数の増加、撹拌翼の大形化が行われている。
【０００４】
従来のこの種の竪形撹拌装置としては、狭幅の横板を複数枚上下に離隔して回転軸に装着した多段パドル型翼をもつもの、あるいはパドル型と格子翼を組み合せた大形翼としたもの、その他大形の枠状翼を有するもの等が知られている。
【０００５】
図２（Ａ）はパドル型と格子翼を組み合せた従来の竪形撹拌翼の１例を示したものであり（特公平１−３７１７３号公報）、円筒形の撹拌槽１の中心に回転軸４が上方へ突出するように設けられ、この回転軸４に該槽１内の処理物（被撹拌物）１０に全体が浸漬する如く撹拌翼２が固着されている。また、撹拌翼２の回転に伴なう処理物１０の上下循環流（後述）を良好にするために槽内側壁に複数本のバッフル３が設けられている。撹拌翼２は回転軸４の下部つまり槽底壁に近接する平板状のボトムパドル５と、ボトムパドル５の上端に該パドル５の回転半径と同じ回転半径をもつ格子翼とを有する。この従来例の格子翼は一対の外側縦材７と一対の内側縦材８とこれらの縦材７，８を連結する上部横材９および中間横材１１によって構成されている。図３（Ａ）の従来例は、前述した図２の撹拌槽１と同じ内径Ｄをもつ撹拌槽１に対して撹拌翼２の回転半径Ｒ_３を図２の例よりも大としたタイプのものである。ボトムパドル５と前記格子翼とを結合した図２の撹拌翼２を、ここではパドル・格子結合撹拌翼と称し、これに対し図３のものを大形結合撹拌翼と称することとする。
【０００６】
また、図４（Ａ）に示すものは特開平４−３４６８２６号公報に記載された枠状翼タイプの撹拌機であり、両側の縦材１３を上下横材１４，１５で連結して枠状翼１２とし、この枠状翼１２の上下横材１４，１５を、円筒状の撹拌槽１の中心に配置された回転軸４に固着した構成としている。両側の縦材１３は下端から上端にかけて回転半径が連続的に小さくなるように傾斜され、槽内壁には両側縦材１３の傾斜外側部と略平行になるように傾斜した複数本のバッフル３が取り付けられている。
【０００７】
【発明が解決しようとする課題】
上述した高液深タイプの竪形撹拌装置の場合、槽の実効内部高さが槽内径より大きくなる（Ｈ／Ｄ＞１．０）につれて処理物の槽内流動において、均一混合を疎外する副循環流の発生（液滞留部や凝縮物の発生をきたす）あるいは共廻り現象の増加等が生じて混合性能が低下するという問題がある。
例えば前述した多段パドル型翼の場合、槽内に不連続に位置する翼が引き起こす個々の流れの相互干渉のため、槽底から液面までを全体として単一流動で循環させるのが困難となり、混合性能が著しく低下する。
【０００８】
また、図２あるいは図３に示すような結合翼あるいは大形結合翼を用いた撹拌装置の場合、下部ボトムパドル５からの液の吐出流が槽内全体にわたる上下循環流を引き起こし、多段パドルよりは優れた混合性能を示すものの、この従来例の構造では液深Ｈと槽内径Ｄとの細長比Ｈ／Ｄが１．５以上になると、液が槽壁を上昇する際に循環流の流速減衰が起こり、槽内全体にわたる上下循環流の形成が困難となり、やはり混合性能の低下は否めない。
【０００９】
また、前述した特開平４−３４６８２６号公報の平板状あるいは枠状の撹拌翼を有する撹拌装置の場合、撹拌翼１２の回転半径を槽１の下部から上部に到るに従い連続的に減少させ、逆にバッフル３の板幅さを槽１の下部から上部にかけて連続的あるいは段階的に増加させて、底部回転半径の大きい撹拌翼１２とバッフル３との相互作用により、循環上昇流の強化により槽内全体に及ぶ上下循環流の形成と短絡流の減少を図っているが、この場合の実例は高々Ｈ／Ｄ＝１．５であり、Ｈ／Ｄ＞１．５となった場合にも有効かどうかは明らかではない。
【００１０】
一方、高粘度液体の混合の場合、槽内の液流動が主循環流と副循環流に別れてしまうことがあり、この副循環流内に液滞留部が発生し易いという問題がある。この副循環流は、低粘度流体でも翼形状と回転速度の相関によって生じることがあり、副循環流の発生により混合時間の遅れ、凝集物／付着物の発生があり、撹拌性能の低下、延いては製品の品質低下、槽内洗浄回数の増加等による生産効率の低下の原因となっている。
【００１１】
また、一般に上下循環流の強化、吐出流の強化を図るため撹拌翼の回転数を増加させた場合、共廻り現象の増加や局所的高剪断場による過剪断あるいは剪断凝集物の形成が起こるため、回転数の極端な増加は望ましくない。さらに後述する如く、上述した従来の撹拌装置はいずれも、細長比Ｈ／Ｄが大となると回転数の増大を必要とし、また、局所的に副循環流が発生し、混合効率が低下する問題があった。
【００１２】
そこで本発明は、細長比Ｈ／Ｄが１．５以上或いは粘度領域が２．０〜３．０Ｐａ・ｓ以上となっても副循環流の発生を防止し、低回転数で強い撹拌力を得ることができ、また混合時間も短縮できる竪型撹拌機を提供することにある。
【００１３】
【課題を解決するための手段】
本発明によれば、竪形円筒形の撹拌槽の中心に槽外から回転可能な回転軸を配置し、該軸の下部に、前記撹拌槽の底壁面と僅かな間隙を有して平板状のボトムパドルを装着し、前記ボトムパドルの上側に縦材と横材を格子状に組み合せた格子翼を装着し、前記撹拌槽の側壁面に、上下方向にのびる複数本の邪魔板を周方向に間隙を有して固着し、前記格子翼の外側部を全体として上方が先細形となるようにその下部から上部にかけて傾斜させた竪型撹拌機が提供される。
【００１４】
【実施例】
次に、本発明を実施例について、図面を参照しつつ、従来例と比較しながら説明する。図１は本発明の実施例に係る竪形撹拌機およびその撹拌槽内の軸方向各位置における吐出流の強さ、上昇流強さを示した図である。円筒形の撹拌槽１の中心部に一部が槽上部へ突出し槽外から回転駆動される回転軸４が配置され、回転軸４に撹拌槽１の底壁面と僅かな間隙を有して平板状のボトムパドル５が装着され、このボトムパドル５の上位部分に縦材と横材からなる格子翼が設けられ、さらに撹拌槽１の内側壁に回転軸４と平行に上下にのびる複数本の邪魔板（バッフル）３が取り付けられていることは、図２、図３の従来例と同じであるが、本発明においては、格子翼が上方へ向うにつれてその外側部の回転半径が連続的に小さくなるように構成されている。
【００１５】
図示の実施例では、格子翼は外側および内側それぞれ２本づつの縦材と、これらの縦材をその上端部および中間部で連結する２本の横材で構成され、各縦材の下端はボトムパドル５の上縁に固着されている。外側縦材の下端はボトムパドル５の外側部位置と一致しており、そこから上端へ向けて回転半径が漸減するように回転軸側へ傾斜しているが、内側縦材は回転軸と平行に真直状態で上下に延びている。なおこの実施例では槽１は図２の従来例と形状、大きさが同じであり、ボトムパドル５の回転半径Ｒ_１ａは図２のボトムパドル５の回転半径Ｒ_２ａより大きく、例えばＲ_２ａの１．２〜１．７倍とし、格子翼の上端の回転半径Ｒ_１ｂは図２の格子翼の回転半径Ｒ_２ｂと同じに設定してある。中間横材の回転半径は図２の中間横材と同一もしくはこれよりやや大きい。なお、上述のようにボトムパドル５の上部に格子翼が結合され、該格子翼の外側縦材が回転軸４側へ向って傾斜していることから、本実施例ではこの撹拌翼を傾斜結合撹拌翼と称する。
【００１６】
ここで、本発明の１つの形態によれば、ボトムパドル５の直径は撹拌槽１の内径Ｄに対し０．５〜０．９Ｄとされる。
また、本発明に係る前記傾斜結合撹拌翼の格子翼部分の上端の直径は、１例として、槽内径Ｄに対し０．３〜０．７Ｄとされる。
【００１７】
図１および図５〜図８を参照すれば、本発明の竪形撹拌槽１における処理物１０の混合は、撹拌槽１内の液体中に浸漬するボトムパドル５と格子翼からなる傾斜結合撹拌翼の回転運動、それによって起こる液体の流動およびこの液体の旋回流動を上下流動に方向転換させる槽内壁に固定されたバッフル３の相互作用により行われる。
【００１８】
撹拌槽１の下部では、大形パドルであるボトムパドル５によって形成される強力な旋回吐出流が形成され、槽内壁側に旋回上昇流域、回転軸４側に下降流域が存在する。
さらに、ボトムパドル５の上位に配置された格子翼部分では、図７に示すように、次の４つの流域Ａ〜Ｄが存在し、これらの相互作用によって高い混合性能を得ている。
（Ａ）旋回上昇流域（主上下循環流）
これはボトムパドル５で発生した旋回上昇流が槽内壁のバッフル３によって旋回成分を上昇流に変換しながら内壁に沿って上昇する上昇流域である。
（Ｂ）下降流域（主上下循環流）
回転軸４に沿って下降する下降流域である。
（Ｃ）渦流外向流域
格子翼前面に発生し、回転遠心力により吐出流となって格子翼域外に流出する外向流域である。
（Ｄ）渦流内向流域
前記格子翼後面に発生し、縦材および横材の格子構造によって発生する渦流と内向流が存在する流域である。
【００１９】
これに対して従来の多段パドルタイプ、大形パドルタイプあるいは大形枠状翼タイプの撹拌装置においては、主として下部で発生させた旋回上昇流による単一上下循環流によって混合が行われる。例えば図４の枠状翼１２の場合、下部の回転半径の大きい部分で大きな吐出流および旋回上昇流を発生させ、中間部では旋回吐出流と内向流をバランスさせることにより、短絡流を防止して、上昇流の保持を図り、枠状翼１２の上面より下降流を発生させている。また、撹拌翼の回転半径を下部から上部にかけて減少させると共に、対向するバッフル３を下部から上部へ向けて増加させることで上昇流の強化を図っている。
【００２０】
一方、図２，図３に示す従来のボトムパドルと格子翼との結合翼タイプの撹拌機においては、下部大形パドルによる強力な吐出流に基づく上下循環流が主体であり、これは図４の従来例と同様であるが、異なる点はこのタイプの撹拌機は格子翼における渦流／混合流による内向／外向の短絡流を逆に利用しているため、上昇流が減衰しても一部が液面まで到達すればよく、他の翼と比較してより低い上昇流強さで均一混合ができることである。なお、図１（Ｂ），図２（Ｂ）および図３（Ｂ）において斜線を施した部分Ｓは格子翼の内側縦材８と横材９，１１との内側格子による吐出力を示し、同図（Ｂ）の符号Ｔの部分は外側縦材７と横材９，１１との外側格子による吐出力を表している。図２（Ｃ）にも示すように図２のパドル・格子結合翼では上昇流強さにおいて混合不良域Ｎが生じる。
【００２１】
ところで細長比Ｈ／Ｄが１．５以上となる高液深の場合、あるいは高粘度液（例えば２．０〜３．０Ｐａ・ｓ以上）を対象とする場合、より強い吐出流強さが必要となる。吐出流強さＦは翼半径Ｒおよび翼回転速度ωの２乗に比例する（Ｆ∝Ｒω^２）が、回転速度ωを増加させることにより、共廻りの増加や、過剪断あるいは剪断凝縮物の生成を起こし易く、好ましくない。そこで、まず図２の翼形状と相似形に翼形状を大形化して翼半径Ｒを増大させたのが図３に示す大形結合翼タイプである。このように翼回転半径を増加させることにより、ボトムパドルの吐出流は増加するが、同時に格子翼の渦流（外向／内向流）域も増大し、逆に旋回上昇流域は減少する。その結果、上部において槽底からの旋回上昇流が格子翼からの外向流に押し切られることになり、図３のように撹拌翼の肩部に副循環流が発生し、混合性能を著しく低下させることになる。図３（Ａ）のＭの領域は（主循環流＋副循環流）の生じている領域である。
【００２２】
本発明は、ボトムパドル部分の翼回転半径を増加させることで、回転速度を上げることなく該ボトムパドルによる吐出流強さを増大させ、格子翼を上端に向けて回転半径を減少させることにより、下部分の上昇流強さを確保し、さらに格子翼の内側縦材を図２と同じに回転軸と平行にして該回転軸に沿った一定の吐出力と下降流を維持するようにした。また、本発明では、流動パターンを示す図９（Ａ）（後述）でも分るように短絡流による混合作用も利用しているので、下部から上部に向っての上昇流強さの減少は他の翼に比べてより大きくてもよく、図４のようにバッフル３の幅を下部から上部にかけて増加させる必要はなく、したがって図２、図３の撹拌槽をそのまま利用できる。
【００２３】
高液深における図２のパドル・格子結合翼、図３の大形結合翼および図１に示す本発明の傾斜結合翼における吐出流の強さ、上昇流の強さ、流動パターンを模型的に比較して示したのが図９（Ａ）〜（Ｄ）である。図９（Ｂ）は図２に示す従来の結合翼の場合、同図（Ｃ）は図３の従来の大形結合翼の場合、同図（Ｄ）は図４の従来の枠状翼による撹拌槽の場合である。図２の結合翼の場合はボトムパドルの吐出力が不足しているため、液面付近での混合性能が悪くなっている。さらに、図３の場合には翼回転半径を大としたことにより、充分な吐出力および上昇流は得られるものの、上部の格子翼の肩部に副循環流が発生し、混合性能を低下させている。これに対し図９（Ａ）の本発明の場合にはこのような副循環流が消滅し、主循環流のみとなっているのが分る。
【００２４】
図１０および図１１は、トレーサ法によって撹拌槽内の液循環時間分布を、図３で説明した従来の大形結合撹拌翼と本発明の場合とで比較して示した図である。図１０の大形結合翼の場合、分布のピークが２〜３箇所見られる。これは副循環流の発生を示唆しており、混合性能を著しく低下させている。一方、図１１の本発明の場合は、分布のピークが１箇所のみとなり、その高さも高くなっている。これは副循環流が消滅して１つの主循環流のみとなったことを示しており、混合時間も短縮化されているのが分る。
【００２５】
図１２に、槽内径（直径）３１０ｍｍ、Ｈ／Ｄ＝１．８６の高液深撹拌槽における各種撹拌翼形状とそれに対する混合性能を比較して示した。図２の結合撹拌翼（図１２ではＮｏ．２）を基準に各翼を比較すると、Ｎｏ．１の５段４５°傾斜パドル翼の場合、混合時間はＮｏ．２とほぼ同じ（１０〜１５秒）であるが、回転速度は２００ｒｐｍと速くなっている。Ｎｏ．３の大形結合翼（図３）の場合は、回転数Ｎは低くなるが、混合時間は１０〜１５秒からわずかに低下し、９〜１２秒となっている。これに対してＮｏ．４の本発明の傾斜結合撹拌翼では、回転数Ｎが最も低く、かつ、混合時間も４〜５秒とほぼ半減している。動力Ｐｖはいずれも変わらない。
【００２６】
【発明の効果】
以上説明したように本発明によれば、撹拌槽底部近くの平板状パドル翼を大形とし、これに結合される格子翼を上方へ向けて回転半径が漸減するようにしたので、細長比Ｈ／Ｄが１．５以上のものでも撹拌翼の回転数を上げることなく液の共廻りを防止でき、大形ボトムパドルによる強い吐出流を確保できる。また格子翼の外側部が先細形に傾斜していることから、副循環流の発生も防止でき、したがって副循環流の滞留部に生じる凝集物／付着物が低減でき、混合性能（均一性、混合時間）を著しく向上させることができた。このように本発明の竪形撹拌機により、製品の品質、生産性および操業安定性の向上を達成できる効果がある。本発明は上述のような細長比の大のものだけでなく、高粘度液体に対しても有効に適用できることは勿論である。
【図面の簡単な説明】
【図１】本発明の実施例に係る竪形撹拌機およびその撹拌槽内の軸方向各位置における吐出流の強さ、上昇流強さを示した図である。
【図２】従来のパドル・格子結合撹拌翼をもつ竪形撹拌機を示した図１と同様の図である。
【図３】従来の大形パドル・格子結合翼をもつ竪形撹拌機を示した図１と同様の図である。
【図４】従来の枠状撹拌翼をもつ竪形撹拌機を示した図１と同様の図である。
【図５】図１のＡ−Ａ線に沿った横断面図である。
【図６】図１のＢ−Ｂ線に沿った横断面図である。
【図７】図１のＡ−Ａ線に沿って取った液の槽内流域を示す横断面図である。
【図８】図１のＢ−Ｂ線に沿って取った液の槽内流域を示す横断面図である。
【図９】撹拌槽における流動形態を本発明と図２、図３および図４の従来の場合とを比較して模型的に示した図である。
【図１０】図３に示す撹拌機における撹拌槽内の液循環時間分布を示す図である。
【図１１】本発明における撹拌槽内の液循環時間分布を示す図である。
【図１２】各種の高液深撹拌槽における混合性能を比較して示した図である。
【符号の説明】
１撹拌槽
２撹拌翼
３バッフル
４回転軸
５ボトムパドル
７外側縦材
８内側縦材
９上部横材
１０処理物
１１中間横材
Ｄ撹拌槽内径
Ｈ液深[0001]
[Industrial applications]
The present invention relates to a stirrer used for stirring various fluids, semi-fluids, powders, and the like in a tank, and particularly to a high liquid depth type in which the ratio of the liquid depth H to the tank inner diameter (diameter) D is 1.5 or more. The present invention relates to a high-viscosity type vertical stirrer having a viscosity range of approximately 2.0 to 3.0 Pa · s or more.
[0002]
[Prior art]
This type of vertical stirring device generally rotates a rotating shaft having a stirring blade in the center of the stirring tank from the outside, and uniformly mixes the fluid by the interaction between the rotating stirring blade and the fluid flow generated by the rotation. Is what you do. A baffle (baffle) having a width of 5 to 15% of the inner diameter of the tank is usually provided on the inner wall of the tank in order to prevent co-rotation of the liquid in the tank and the stirring blade and to convert the rotational flow of the fluid into a vertical flow. Are attached at a distance of 2 to 4 or more in the circumferential direction.
[0003]
Conventionally, in a vertical stirrer, the thickness of the tank is reduced when the stirring tank is a high-pressure vessel, and the heat transfer area is increased when the stirring tank is also used as a reaction vessel. In order to reduce the size, a high liquid-depth type in which the height of the tank is larger than the inner diameter D of the tank (liquid depth H / inner diameter D of 1.5 or more) is known. In the case of such a high liquid-depth type or a high-viscosity fluid, the number of revolutions of the blade is increased and the size of the stirring blade is increased in order to enhance the stirring force.
[0004]
Conventional vertical stirrers of this type include multi-stage paddle-type blades with a plurality of narrow horizontal plates vertically separated from each other and mounted on a rotating shaft, or large-size blades combining a paddle type and lattice blades. And those having large frame-shaped wings are known.
[0005]
FIG. 2A shows an example of a conventional vertical stirring blade in which a paddle type and a lattice blade are combined (Japanese Patent Publication No. 1-37373), and a rotary shaft is provided at the center of a cylindrical stirring tank 1. A stirring blade 2 is fixed to the rotating shaft 4 such that the stirring blade 2 is entirely immersed in a processing object (object to be stirred) 10 in the tank 1. Also, a plurality of baffles 3 are provided on the inner wall of the tank in order to improve the vertical circulation flow (described later) of the processing object 10 accompanying the rotation of the stirring blade 2. The stirring blade 2 has a flat bottom paddle 5 adjacent to the lower part of the rotary shaft 4, that is, the bottom wall of the tank, and a lattice blade having a rotation radius equal to the rotation radius of the paddle 5 at the upper end of the bottom paddle 5. The lattice wing of this conventional example is constituted by a pair of outer vertical members 7, a pair of inner vertical members 8, an upper horizontal member 9 connecting these vertical members 7, and an intermediate horizontal member 11. Conventional example of FIG. 3 (A), the type of which is larger than the example of FIG. 2 the turning radius R ₃ of the stirring blade 2 with respect to the stirred tank 1 having the same inner diameter D and the stirred tank 1 in FIG. 2 described above Things. The stirring blade 2 of FIG. 2 in which the bottom paddle 5 and the lattice blade are combined is referred to as a paddle / grid coupled stirring blade here, whereas the one shown in FIG. 3 is referred to as a large combined stirring blade.
[0006]
FIG. 4A shows a frame-shaped blade-type stirrer described in JP-A-4-346826, in which vertical members 13 on both sides are connected by upper and lower horizontal members 14 and 15 to form a frame. The blade 12 is configured such that the upper and lower cross members 14 and 15 of the frame-shaped blade 12 are fixed to the rotating shaft 4 arranged at the center of the cylindrical stirring tank 1. The vertical members 13 on both sides are inclined so that the radius of rotation is continuously reduced from the lower end to the upper end, and a plurality of baffles 3 inclined on the inner wall of the tank so as to be substantially parallel to the inclined outer portions of the vertical members 13 on both sides. Installed.
[0007]
[Problems to be solved by the invention]
In the case of the vertical stirrer of the above-mentioned high liquid depth type, as the effective internal height of the tank becomes larger than the inner diameter of the tank (H / D> 1.0), a sub-unit for avoiding uniform mixing in the flow of the processing object in the tank. There is a problem that the mixing performance is reduced due to the generation of a circulating flow (which causes the generation of a liquid stagnation portion or condensate) or an increase in the co-rotation phenomenon.
For example, in the case of the multi-stage paddle-type blade described above, it is difficult to circulate a single flow as a whole from the tank bottom to the liquid level due to mutual interference of individual flows caused by blades discontinuously positioned in the tank, Mixing performance is significantly reduced.
[0008]
In the case of a stirrer using a connection blade or a large connection blade as shown in FIG. 2 or FIG. 3, the discharge flow of the liquid from the lower bottom paddle 5 causes a vertical circulating flow over the entire tank, and Shows excellent mixing performance, but in the structure of this conventional example, when the slenderness ratio H / D between the liquid depth H and the inside diameter D of the tank becomes 1.5 or more, the flow rate of the circulating flow when the liquid rises up the tank wall Attenuation occurs, making it difficult to form a vertical circulating flow over the entire inside of the tank.
[0009]
Further, in the case of the stirring device having a flat or frame-shaped stirring blade described in JP-A-4-346826 described above, the radius of rotation of the stirring blade 12 is continuously reduced from the lower part to the upper part of the tank 1, Conversely, the plate width of the baffle 3 is increased continuously or stepwise from the lower part to the upper part of the tank 1, and the interaction between the agitating blade 12 having a large bottom turning radius and the baffle 3 enhances the circulation upward flow to increase the tank width. The formation of the vertical circulation flow and the reduction of the short-circuit flow over the entire inside are attempted, but in this case, H / D = 1.5 at most, and it is effective even when H / D> 1.5. It is not clear whether it is.
[0010]
On the other hand, in the case of mixing a high-viscosity liquid, the liquid flow in the tank may be divided into a main circulation flow and a sub circulation flow, and there is a problem that a liquid stagnation portion is easily generated in the sub circulation flow. This sub-circulation flow may occur due to the correlation between the blade shape and the rotation speed even with a low-viscosity fluid. The generation of the sub-circulation flow delays the mixing time, generates agglomerates / adhered matter, lowers the stirring performance, and increases the In addition, it causes a decrease in product efficiency and a decrease in production efficiency due to an increase in the number of washings in the tank.
[0011]
Also, in general, when the rotation speed of the stirring blade is increased to strengthen the vertical circulation flow and the discharge flow, the co-rotation phenomenon increases and over-shearing or formation of shear aggregates due to local high shearing fields occur. However, an extreme increase in the number of revolutions is undesirable. As will be described later, all of the above-described conventional stirring devices require an increase in the number of revolutions when the slenderness ratio H / D is large, and a local circulation flow is generated locally, resulting in a decrease in mixing efficiency. was there.
[0012]
Therefore, the present invention prevents the generation of the auxiliary circulation flow even when the slenderness ratio H / D is 1.5 or more or the viscosity region is 2.0 to 3.0 Pa · s or more, and provides a strong stirring force at a low rotation speed. An object of the present invention is to provide a vertical stirrer which can be obtained and can shorten the mixing time.
[0013]
[Means for Solving the Problems]
According to the present invention, a rotary shaft rotatable from the outside of the tank is disposed at the center of the vertical cylindrical stirring tank, and a flat plate having a small gap with the bottom wall surface of the stirring tank below the shaft. The bottom paddle is mounted, and a lattice blade in which a vertical member and a horizontal member are combined in a lattice shape is mounted on the upper side of the bottom paddle, and a plurality of baffles extending vertically in the side wall surface of the stirring tank are circumferentially mounted. A vertical stirrer is provided which is fixed from the lower part to the upper part such that the upper part of the lattice blade is tapered as a whole.
[0014]
【Example】
Next, embodiments of the present invention will be described with reference to the drawings and in comparison with conventional examples. FIG. 1 is a diagram showing a vertical stirrer according to an embodiment of the present invention and the strength of a discharge flow and the strength of an upward flow at respective axial positions in the stirring tank. At the center of the cylindrical stirring tank 1, there is disposed a rotating shaft 4 which partially projects to the upper part of the tank and is driven to rotate from the outside of the tank, and the rotating shaft 4 is flat with a slight gap from the bottom wall surface of the stirring tank 1. The bottom paddle 5 is mounted, and a lattice wing composed of a vertical member and a horizontal member is provided on an upper portion of the bottom paddle 5, and a plurality of vertically extending parallel to the rotating shaft 4 is provided on an inner wall of the stirring tank 1. The baffle plate (baffle) 3 is attached in the same manner as in the conventional example shown in FIGS. 2 and 3, but in the present invention, as the lattice wings move upward, the radius of rotation of the outer side thereof increases continuously. It is configured to be smaller.
[0015]
In the illustrated embodiment, the lattice wing is made up of two longitudinal members each on the outside and inside, and two cross members connecting these longitudinal members at the upper end and the middle part, and the lower end of each longitudinal member is The bottom paddle 5 is fixed to the upper edge. The lower end of the outer longitudinal member coincides with the position of the outer part of the bottom paddle 5 and is inclined toward the rotating shaft so that the radius of rotation gradually decreases from there toward the upper end, but the inner longitudinal member is parallel to the rotating shaft. It extends up and down in a straight state. Incidentally tank 1 in this embodiment is conventional and shape of FIG. 2, the magnitude is the same, the rotation radius R _1a of the bottom paddle 5 is larger than the rotational radius R _2a of the bottom paddle 5 in FIG. 2, for example, the R _2a The rotation radius R _{1b at} the upper end of the lattice blade is set to be the same as the rotation radius R _2b of the lattice blade in FIG. 2. The turning radius of the intermediate cross member is the same as or slightly larger than that of the intermediate cross member in FIG. In addition, since the lattice blade is connected to the upper part of the bottom paddle 5 as described above, and the outer longitudinal member of the lattice blade is inclined toward the rotation shaft 4, the stirring blade is connected to the inclined blade in this embodiment. It is called a stirring blade.
[0016]
Here, according to one embodiment of the present invention, the diameter of the bottom paddle 5 is set to 0.5 to 0.9 D with respect to the inner diameter D of the stirring tank 1.
Further, the diameter of the upper end of the lattice blade portion of the inclined coupling stirring blade according to the present invention is, for example, 0.3 to 0.7 D with respect to the tank inner diameter D.
[0017]
Referring to FIG. 1 and FIG. 5 to FIG. 8, the mixing of the processed material 10 in the vertical stirring tank 1 of the present invention is performed by a tilted stirrer composed of a bottom paddle 5 immersed in a liquid in the stirring tank 1 and a lattice blade. Rotational movement of the wings, the resulting liquid flow and the interaction of the baffle 3 fixed to the inner wall of the tank that turns the swirling flow of the liquid into a vertical flow.
[0018]
In the lower part of the stirring tank 1, a strong swirling discharge flow formed by the bottom paddle 5 which is a large paddle is formed, and a swirling upward flow area exists on the inner wall side of the tank and a downward flow area exists on the rotating shaft 4 side.
Further, in the lattice wing portion arranged above the bottom paddle 5, as shown in FIG. 7, the following four water basins A to D exist, and high mixing performance is obtained by their interaction.
(A) Swirling upflow area (main vertical circulation flow)
This is an ascending flow region in which the swirling upward flow generated by the bottom paddle 5 rises along the inner wall while converting the swirling component into an upward flow by the baffle 3 on the inner wall of the tank.
(B) Downward basin (main vertical circulation flow)
This is a descending flow region descending along the rotation axis 4.
(C) Outward vortex flow area This is an outward flow area generated on the front face of the lattice blade and discharged as a discharge flow due to the rotational centrifugal force and out of the lattice blade area.
(D) Inward swirl flow region This is a flow region that is generated on the rear surface of the lattice blade and has a swirl flow and an inward flow generated by the lattice structure of the vertical members and the horizontal members.
[0019]
On the other hand, in a conventional multistage paddle type, large paddle type or large frame type blade type stirring device, mixing is performed by a single vertical circulating flow mainly by a swirling upward flow generated at a lower portion. For example, in the case of the frame-shaped wing 12 shown in FIG. 4, a large discharge flow and a swirling upward flow are generated at a lower portion of a large turning radius, and a short-circuit flow is prevented by balancing the swirl discharge flow and the inward flow at an intermediate portion. Thus, the upward flow is maintained, and a downward flow is generated from the upper surface of the frame-shaped wing 12. In addition, the radius of rotation of the stirring blade is reduced from the lower part to the upper part, and the baffle 3 facing the upper part is increased from the lower part to the upper part, thereby enhancing the upward flow.
[0020]
On the other hand, in the conventional stirrer of the combined blade type composed of the bottom paddle and the lattice blade shown in FIGS. 2 and 3, a vertical circulating flow based on a strong discharge flow by the large paddle is mainly used. However, this type of agitator uses the inward / outward short circuit flow due to the vortex / mixed flow in the lattice blades in reverse, so that even if the ascending flow is attenuated, Suffices to reach the liquid level, and uniform mixing can be performed with a lower rising flow intensity compared to other blades. In FIG. 1 (B), FIG. 2 (B) and FIG. 3 (B), the hatched portion S indicates the discharge force of the inner vertical member 8 and the horizontal members 9 and 11 of the lattice wing by the inner lattice. The portion indicated by the symbol T in FIG. 3B represents the discharge force by the outer grid of the outer vertical member 7 and the horizontal members 9 and 11. As shown in FIG. 2 (C), in the paddle / lattice-coupled blade of FIG. 2, a poor mixing region N occurs at the rising flow strength.
[0021]
By the way, in the case of a high liquid depth where the slenderness ratio H / D is 1.5 or more, or in the case of a high viscosity liquid (for example, 2.0 to 3.0 Pa · s or more), a stronger discharge flow strength is required. It becomes. The discharge flow intensity F is proportional to the square of the blade radius R and the blade rotation speed ω (F∝Rω ² ), but by increasing the rotation speed ω, an increase in co-rotation and an increase in over-shear or shear condensate It is easy to produce and is not preferred. Therefore, the large combined blade type shown in FIG. 3 first increases the blade radius R by increasing the blade shape to a shape similar to the blade shape of FIG. By increasing the blade turning radius in this way, the discharge flow of the bottom paddle increases, but at the same time, the swirl (outward / inward flow) region of the lattice blade also increases, and conversely, the swirl rising flow region decreases. As a result, the swirling upward flow from the tank bottom at the upper part is pushed out by the outward flow from the lattice blade, and a sub-circulating flow is generated at the shoulder of the stirring blade as shown in FIG. Will be. A region M in FIG. 3A is a region where (main circulation flow + sub circulation flow) occurs.
[0022]
The present invention increases the blade turning radius of the bottom paddle portion, thereby increasing the discharge flow strength by the bottom paddle without increasing the rotation speed, and reducing the turning radius by directing the lattice blade toward the upper end. The upward flow strength of the lower part was secured, and the vertical members inside the lattice blades were made parallel to the rotation axis in the same manner as in FIG. 2 so as to maintain a constant discharge force and a downward flow along the rotation axis. Further, in the present invention, as can be seen from FIG. 9A (which will be described later) showing the flow pattern, the mixing action by the short-circuit flow is also used. It is not necessary to increase the width of the baffle 3 from the lower part to the upper part as shown in FIG. 4, so that the stirring tank shown in FIGS. 2 and 3 can be used as it is.
[0023]
The strength of the discharge flow, the strength of the upward flow, and the flow pattern of the paddle / grid coupling blade of FIG. 2, the large coupling blade of FIG. 3, and the inclined coupling blade of the present invention shown in FIG. FIGS. 9A to 9D show the comparison. 9 (B) shows the case of the conventional connecting blade shown in FIG. 2, FIG. 9 (C) shows the case of the conventional large connecting blade of FIG. 3, and FIG. 9 (D) shows the case of the conventional frame-shaped blade of FIG. This is the case of a stirring tank. In the case of the combined blade shown in FIG. 2, the mixing performance near the liquid level is deteriorated because the discharge force of the bottom paddle is insufficient. Further, in the case of FIG. 3, by increasing the blade turning radius, although a sufficient discharge force and ascending flow can be obtained, a secondary circulation flow is generated at the shoulder of the upper lattice blade, and the mixing performance is reduced. ing. On the other hand, in the case of the present invention shown in FIG. 9A, such a sub-circulation flow disappears and only the main circulation flow is seen.
[0024]
FIGS. 10 and 11 are diagrams showing the distribution of liquid circulation time in the stirring tank by the tracer method in comparison with the conventional large combined stirring blade described in FIG. 3 and the case of the present invention. In the case of the large coupling wing of FIG. 10, two or three distribution peaks are observed. This indicates the occurrence of a sub-circulation flow, which significantly reduces the mixing performance. On the other hand, in the case of the present invention shown in FIG. 11, the distribution has only one peak, and the height is high. This indicates that the sub-circulation flow has disappeared to only one main circulation flow, and it can be seen that the mixing time has also been reduced.
[0025]
FIG. 12 shows various stirring blade shapes in a high liquid depth stirring tank having a tank inner diameter (diameter) of 310 mm and H / D = 1.86 and a mixing performance thereof. Comparing each blade based on the combined stirring blade (No. 2 in FIG. 12) of FIG. In the case of the 5-stage 45 ° inclined paddle blade of No. 1, the mixing time was No. 2, but the rotation speed is as fast as 200 rpm. No. In the case of the large combined blade 3 (FIG. 3), the number of revolutions N is low, but the mixing time is slightly reduced from 10 to 15 seconds to 9 to 12 seconds. On the other hand, No. In the inclined coupling stirring blade of No. 4 of the present invention, the rotation speed N is the lowest, and the mixing time is almost halved to 4 to 5 seconds. The power Pv does not change.
[0026]
【The invention's effect】
As described above, according to the present invention, the flat paddle blade near the bottom of the stirring tank is made large, and the lattice radiator connected thereto is configured so that the radius of gyration gradually decreases upward. Even when the ratio / D is 1.5 or more, the rotation of the liquid can be prevented without increasing the rotation speed of the stirring blade, and a strong discharge flow by the large bottom paddle can be secured. In addition, since the outer portion of the lattice blade is tapered, it is possible to prevent the generation of the sub-circulation flow, so that the agglomerates / adhering matter generated in the stagnation portion of the sub-circulation flow can be reduced, and the mixing performance (uniformity, uniformity, Mixing time) could be significantly improved. As described above, the vertical stirrer of the present invention has an effect of improving the quality, productivity, and operation stability of a product. Of course, the present invention can be effectively applied not only to the liquid having a large slenderness ratio as described above, but also to a high-viscosity liquid.
[Brief description of the drawings]
FIG. 1 is a view showing a vertical stirrer according to an embodiment of the present invention and the strength of a discharge flow and the strength of an upward flow at respective axial positions in the stirring tank.
FIG. 2 is a view similar to FIG. 1 showing a conventional vertical stirrer having a paddle / lattice-coupled stirring blade.
FIG. 3 is a view similar to FIG. 1 showing a conventional vertical stirrer having a large paddle / grid coupling blade.
FIG. 4 is a view similar to FIG. 1 showing a conventional vertical stirrer having a frame-shaped stirring blade.
FIG. 5 is a transverse sectional view taken along the line AA of FIG. 1;
FIG. 6 is a transverse sectional view taken along line BB of FIG. 1;
FIG. 7 is a cross-sectional view showing a flow area in the tank of the liquid taken along line AA in FIG. 1;
FIG. 8 is a cross-sectional view showing the flow area in the tank of the liquid taken along the line BB in FIG. 1;
FIG. 9 is a diagram schematically showing a flow form in a stirring tank in comparison with the present invention and the conventional cases of FIGS. 2, 3 and 4.
10 is a view showing a liquid circulation time distribution in a stirring tank in the stirrer shown in FIG.
FIG. 11 is a diagram showing a liquid circulation time distribution in a stirring tank in the present invention.
FIG. 12 is a diagram showing a comparison of mixing performance in various high liquid depth stirring tanks.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 stirring tank 2 stirring blade 3 baffle 4 rotating shaft 5 bottom paddle 7 outer vertical member 8 inner vertical member 9 upper horizontal member 10 processed material 11 intermediate horizontal member D stirring tank inner diameter H liquid depth

Claims

A rotating shaft rotatable from the outside of the tank is disposed at the center of the vertical cylindrical stirring tank, and a flat bottom paddle having a slight gap with the bottom wall surface of the stirring tank is mounted below the shaft. On the upper side of the bottom paddle, a lattice blade in which vertical members and horizontal members are combined in a lattice shape is mounted, and on the side wall surface of the stirring tank, a plurality of baffle plates extending in the vertical direction are provided with a circumferential gap. A vertical stirrer fixedly attached and inclined from a lower portion to an upper portion so that the entire outer portion of the lattice blade is tapered upward as a whole.

The lattice wing has an outer inclined longitudinal member having a lower end in contact with an outer portion of the bottom paddle and having a continuously decreasing radius of rotation toward an upper end, and an inner longitudinal member having a constant rotating radius parallel to the rotation axis. The vertical stirrer according to claim 1, comprising:

Vertical type as described in the rotational diameter (diameter) inside diameter of the D ₁ the stirred tank (diameter) first claims, characterized in that the 0.5~0.9D D or paragraph 2 of the bottom paddle mixer.

The agitation tank, when the liquid depth H, the inner diameter (diameter) is D, is substantially H / D> 1.5, 0.3~ rotational diameter (diameter) _{D 2} of the upper end of the lattice blade The vertical stirrer according to any one of claims 1 to 3, wherein the vertical stirrer is 0.7D.